Wet processing (i.e. the exposure of a surface or surfaces to a fluid or fluids) is an essential part of many technologies. In particular, semiconductor, micro-electro-mechanical systems (MEMS, also known as micro systems, among other names), photovoltaic technologies rely heavily on wet processes for the manufacturing of devices. Processes such as etching, resist developing, patterning, stripping, release, electroplating, and thinning are all usually performed by the exposure of surfaces to liquids; i.e. wet processing.
One of the main drawbacks of all prior art is the reliance of wet processes on immersion of the parts in a liquid, on some form of spraying, or in a combination of liquid delivery and substrate spinning, to accomplish the exposure of the surface to the liquid. These methods, and their many variants, usually expose, at least to a relevant extent, other surfaces that would be desirable to protect from the fluid. To prevent unwanted exposure of surfaces. The prior art has usually relied on the application of protective layers, or resists.
As fabrication technologies advance and higher functionality and feature densities are a major driver of systems performance and lower prices; a true single sided wet process would provide additional process flexibility and allow a higher level of integration. In particular, features or devices could be in a finished state on one side while wet processing could continue on the other side without jeopardizing its integrity by wetting it or otherwise exposing it to the fluid or its vapors, using resists, masks or other forms of protection.
There are wet processing systems that attempt to perform single sided wet processing, that is, even though the exposure takes place primarily on one side, it usually exposes the other side to relevant levels of mist or vapor. Such exposure is sufficient to either disqualify such systems for single sided processing, or merit the use of resists or other forms of protection to prevent damage to the side not being processed.
However, the present invention is capable of single-sided processing without exposing the backside of the surface in process, thus enabling a great variety of novel processes and new levels of device integration, among other things. It is clear that all applications and implications of the present invention are not all listed here, but, nevertheless, are also a part of this invention.
Furthermore, due to the present invention's intrinsic virtual decoupling of transport phenomena from the action of the fluid, the present invention improves upon attainable uniformity as compared to conventional arrangements. This may be of particular importance in processes that remove material off of the substrate's surface by the action or contact with the fluid. Such applications include, e.g., etching, thinning, developing, among others. This uniformity improvement can be up to ten times better than that which can be attained with conventional arrangements, e.g., spin, spray or immersion etching, etc., depending on the particulars of the process.